Comparison of the inhibitory activities of human tissue factor pathway inhibitor (TFPI)α and TFPIβ

Abstract

Summary Background Tissue factor pathway inhibitor (TFPI) is an alternatively spliced protein with two isoforms, TFPIα and TFPIβ, which differ in their carboxy-terminal structure and cellular localization. Detailed characterization of their inhibitory activity is needed to define potentially unique inhibitory roles in tissue factor (TF) mediated thrombotic and inflammatory disease and to understand how pharmaceuticals targeted to different structural regions of the TFPI isoforms alter hemostasis in hemophilia patients. Methods The TF inhibitory activity of TFPIβ localized to the surface of CHO cells was compared to soluble TFPIα using in vitro and in vivo assays. Results In TF-FVIIa-mediated FXa generation assays, TFPIβ was a slightly better inhibitor than TFPIα, which was ~3-fold better than TFPI- 160, a soluble, altered form of TFPI similar to TFPIβ. In direct FXa inhibitory assays, TFPIβ had an IC50 2.5-fold lower than TFPIα and 56-fold lower than TFPI-160. TFPIβ inhibited TF-mediated CHO cell migration though Matrigel, while TFPIα or TFPI-160 were poor inhibitors, demonstrating that TFPIβ effectively blocks TF-initiated signaling events during cellular migration through matrices not permeable to soluble forms of TFPI. Further, TFPIβ inhibited TF-dependent CHO cell infiltration into lung tissue following tail vein injection into SCID mice and blocked development of consumptive coagulopathy. Conclusions When compared to TFPIα, TFPIβ is a slightly better inhibitor of TF procoagulant activity. As a surface associated protein, TFPIβ is a much better inhibitor of TF-mediated cellular migration than soluble TFPIα and may distinctly act in the inhibition of TF-mediated signaling events on inflamed endothelium and/or monocytes.

Expression of Human Tissue Factor Pathway Inhibitor on Vascular Smooth Muscle Cells Inhibits Secretion of Macrophage Migration Inhibitory Factor and Attenuates Atherosclerosis in ApoE −/− Mice

“…TFPIβ inhibits TF-mediated thrombin generation better than either TFPIα or a soluble truncated form of TFPI (TFPI-160) similar to TFPIβ, suggesting that cell surface association plays an important role in efficient inhibition of TF. 24 Conversely, K3 and the C-terminal region of TFPIα significantly enhance FXa inhibitory activity without having direct protease inhibitor activity themselves. 24 The fusion protein combines both cell-tethering and K3 effects and therefore acts as a highly efficient inhibitor of TF.…”

“…24 Conversely, K3 and the C-terminal region of TFPIα significantly enhance FXa inhibitory activity without having direct protease inhibitor activity themselves. 24 The fusion protein combines both cell-tethering and K3 effects and therefore acts as a highly efficient inhibitor of TF.…”

Biology of tissue factor pathway inhibitor

“…2014;123(19): [2934][2935][2936][2937][2938][2939][2940][2941][2942][2943] Tissue factor (TF) pathway inhibitor (TFPI) is the primary inhibitor of the initiation of blood coagulation and modulates the severity of a wide variety of bleeding and clotting disorders. TFPI impedes the early stages of the blood coagulation cascade through high-affinity inhibition of 2 coagulation proteases, TF-factor VIIa (TF-FVIIa) [1][2][3] and factor Xa (FXa). 2,3 This review is focused on the 2 major isoforms of TFPI: TFPIa and TFPIb.…”

“…TFPI impedes the early stages of the blood coagulation cascade through high-affinity inhibition of 2 coagulation proteases, TF-factor VIIa (TF-FVIIa) [1][2][3] and factor Xa (FXa). 2,3 This review is focused on the 2 major isoforms of TFPI: TFPIa and TFPIb. These isoforms differ in their affinity for factor V/Va (FV/FVa) 4,5 and protein S (PS), 6-9 their tissue expression, 10-13 their mechanism for association with cell surfaces, [14][15][16][17] and their ability to impede early blood coagulation through inhibition of TF-FVIIa activity 3 or inhibition of prothrombinase activity.…”

“…2,3 This review is focused on the 2 major isoforms of TFPI: TFPIa and TFPIb. These isoforms differ in their affinity for factor V/Va (FV/FVa) 4,5 and protein S (PS), 6-9 their tissue expression, 10-13 their mechanism for association with cell surfaces, [14][15][16][17] and their ability to impede early blood coagulation through inhibition of TF-FVIIa activity 3 or inhibition of prothrombinase activity. 5 Following vascular injury, TF is exposed to the blood and tightly binds the circulating serine protease FVIIa, 18-20 increasing FVIIa catalytic activity by ;30 000-fold.…”